The mass-market version of the World Wide Web has been around for, oh, a dozen or so years now. In all that time, advertising and marketing types still haven’t figured out a solid way to monetize digital media for the same impact as print, radio or television.

Yeah, there’s Google AdSense and other syndicates. Plus plenty of examples of the success of online campaigns and viral marketing. But they’re all fairly isolated, and a drop in the bucket compared to the overall media advertising picture, future trending notwithstanding.

So it’s no surprise that online video, the latest Web content frontier, is similarly bedeviling Madison Avenue (and beyond).

There is an interesting concept sprouting out of the approach toward capturing monitor-glued eyeballs:

During a recent episode of “Lost” on ABC’s Web site, for instance, Taco Bell offered a virtual photo shoot with Sports Illustrated swimsuit model Daniella Sarahyba.

As viewers watch video of Sarahyba on location, they use the mouse to move around and snap up to 100 shots. Afterward, viewers can download the photos (with a Taco Bell logo in the corner), choose another locale or resume the show without missing a second.

“It becomes a lean-in experience rather than just a lean-back,” said Shawn Chapman, senior manager for brand communications at Yum Brands Inc.’s Taco Bell chain. “I think consumers give us credit for doing things a little bit differently.”

“Leaning-in” — meaning compelling Web viewers to focus attention and give undivided attention — instead of the default “leaning-back”, which conveys the usual multi-tasking passivity with which most people interact online (and, incidentally, with television). It’s a great shorthand for goal achievement.